1. Field of the Invention
The present invention relates to an earthquake monitoring device and a method of installing the same, and more particularly, to an earthquake monitoring device and a method of installing the same, which can permit stable and efficient installation and operation on any ground surface with free-field conditions including level and sloped ground conditions, and can provide precise monitoring results of earthquakes.
2. Description of the Related Art
Recently, as earthquakes frequently cause catastrophic damage, social concern over earthquakes is gradually increasing. For the purpose of early warning and rapid response to earthquakes, earthquake monitoring for major sites and facilities has been rapidly expanded to apply various options and obtain data.
Such earthquake monitoring is performed to measure velocity or acceleration as major monitoring targets at a monitoring location upon an earthquake. Earthquake monitoring using a seismometer is essentially intended to investigate quantitative phenomena of an earthquake and thus is also classified as seismic observation. Most seismometers are operated at a location generating very insignificant noise, if any, and are thus placed in bedrock located at a deep depth or in desolate mountains and tunnels. Unlike seismometers, accelerometers are relatively cheap and serve to monitor an earthquake under living conditions. Thus, the accelerometers have been broadly placed on major facilities or surrounding sites.
Generally, recent earthquake monitoring instruments can be classified into a sensor for detecting vibration signals such as in an earthquake and a recorder for recording such signals. In recent years, a data transmission apparatus based on wired and wireless communication techniques may be additionally connected to the earthquake monitoring instruments, or a data transmission function may be incorporated into the recorder. The sensor which initially senses seismic signals from outside is provided therein with a vibration measurement device designed to monitor an earthquake in terms of three components on the orthogonal coordinate, in which the three components include a longitudinal component, a transverse component, and a vertical component. Generally, the sensor is placed such that these components collide with the north-south direction, the east-west direction, and the direction of gravity, respectively. The sensor typically has a circular shape in plan view and can be made in a substantially quadrangular shape or various other shapes.
Earthquake monitoring can provide data for earthquake alert and response and can also be utilized as a fundamental resource for earthquake-resistant design based on accumulation of such data and establishment of databases. Therefore, monitoring reliability in various fields can be ensured based on reliable installation and operation. In addition, since the seismometers and accelerometers are very expensive as compared with other measuring devices and must be operated for a long time once installed, they must be appropriately placed to provide reasonable data so as to ensure economic feasibility.
Nevertheless, inadequate installation and operation of such monitoring devices are made on many monitoring target locations, causing serious economic loss and use of erroneous earthquake monitoring data. For an earthquake monitoring device, many sensors are inadequately installed or operated. Generally, instead of being directly exposed to an external environment, the recorder is placed and operated in a stable indoor environment and is made in a standard form, and thus incorrect installation and operation of the recorder hardly occurs. However, although sensors are used together with a variety type of accessories or through partial modification of monitoring locations when placed at a site or facility to be monitored, thereby requiring high technical knowledge, the sensors are generally installed by unskilled laborers, causing critical mistakes. Therefore, there is an urgent need for a systematic technology associated with installation and operation of the earthquake monitoring sensor in order to prevent serious mistakes in installation and operation and to provide reliable earthquake monitoring data such that efficient earthquake alert and response and reasonable earthquake-resistant designs can be obtained. In addition, since many earthquake monitoring sensors are directly exposed to natural environments, there is a need for environmentally friendly installation thereof.
In general, the earthquake monitoring sensors are placed at various locations, such as ground surfaces, or surfaces of elements or members inside or outside facilities, so as to be exposed to an atmosphere (i.e., air) in a natural state and to have verticality through base work and level adjustment by taking azimuths into account. Exceptionally, when earthquake monitoring is performed through a borehole which entails enormous cost, the sensor does not have a free-field which allows the sensor to contact the atmosphere. In this case, since experts in the field of seismology or earthquake engineering generally participate in planning, installation and operation for such earthquake monitoring, there is substantially no error in obtaining data.
On the contrary, earthquake monitoring using sensors installed in a free-field are relatively inexpensive and commonly used. Accordingly, this type of sensor is generally accepted in the art and thus is frequently installed by unskilled persons instead of experts in seismology or earthquake engineering, thereby causing mistakes in installation and operation.
A typical serious mistake frequently occurring in free-field earthquake monitoring is that earthquake monitoring is performed with respect to different locations or conditions providing significantly different seismic response instead of being performed with respect to a monitoring target location to be considered in practice.
As shown in FIG. 1 which is a diagram illustrating typical mistake cases, although earthquake monitoring data associated with free-field ground surfaces of the ground are demanded as impotent data to be used in the field of seismology or earthquake engineering, earthquake monitoring is performed on completely different locations or conditions caused by excavation or additional concrete support, and the resultant data are used as desired data measured on the ground surface. If data measured according to FIG. 1 are used for earthquake-resistant design or earthquake-resistant performance evaluation, seriously underrated or overrated designs and evaluation can be incurred. In addition, as partially shown in FIG. 1, a protective device or base for the earthquake monitoring sensor is neither considered nor employed. As a result, frequent failure and reduction in lifespan of the earthquake monitoring sensor and errors in measurement data in combination with external factors can be incurred.